Renewable energy such as wind generation which does not generate carbon dioxide during operation in contrast to a power-generation plant such as a conventional thermal power generation system which burns fossil fuel is becoming more popular from a viewpoint of suppressing global warming. As a type of such alternative energy, solar power generation which is power generation by heating a heat medium with heat obtained by collecting sunlight and driving a turbine by using heat capacity of the heat medium as an energy source is attracting attention. Solar power generation can be carried out by utilizing a technique and a facility similar to those of the conventional thermal power generation system and it is possible to obtain higher output from the solar power generation than from other types of renewable energy.
As a light collecting solar power generation system, some types of systems including a trough type, a tower type, and a dish type have been developed. The system basically obtains energy by collecting the sunlight to a high density and includes mirrors for reflecting the sunlight, a heat receiving unit for receiving the reflected light and transferring the heat to a heat medium, and an energy converting system such as a steam generator and a turbine/power generator.
Because higher power generation efficiency is obtained in the light collecting solar power generation system when an upstream temperature in a turbine cycle, i.e., a temperature of the heat medium is higher, increase of a heat transfer coefficient in the heat receiving unit is desired.